ANISOTROPIC CRITICAL-CURRENT DENSITIES OF SILVER-SHEATHED BSCCO-2223 TAPE

A novel experimental arrangement is described in which current is cons trained to flow perpendicular to the faces of (Bi, Pb)2Sr2Ca2Cu3Ox sil ver clad tape produced by the standard powder in tube technique. This configuration with ''perpendicular'' current flow shows that significa nt voltages are developed at current densities less than 1% of the con ventional, longitudinal, critical current density. The effect of appli ed magnetic fields on the perpendicular critical current density are a lso reported, with fields perpendicular to the plane of the tape being most effective at reducing the critical current density. From this da ta it is calculated that the average critical current of each grain bo undary is 0.5 mA and < 10 muA for the longitudinal and perpendicular f lows respectively. This difference is attributed to the perpendicular current probing the whole of the superconductor core, whilst the longi tudinal current may flow predominantly in a higher critical current de nsity region near the silver sheath; Implications for the current dist ribution and critical current density measurement in short samples of BSCCO-2223 tape are considered.